Dark Matter Annihilation Flux

Expected gamma-ray signal from WIMP annihilation in Ο‰Cen's dark matter halo β€” compared to Fermi-LAT upper limits and CTA projected sensitivity.

πŸ”¬ Established Astrophysics ⚠ DM Particle Model
Why Ο‰Cen? Ο‰Centauri is likely the stripped nucleus of a dwarf galaxy (see dark matter context). Stripped dwarfs can retain a dark matter cusp β€” a dense central concentration that dramatically boosts annihilation flux. The predicted J-factor for Ο‰Cen makes it competitive with known dwarf spheroidals as a DM search target.
⚠ No confirmed detection. Dark matter annihilation has not been observed in Ο‰Cen or any other source. All flux values are model predictions. Fermi-LAT has published upper limits; this tool shows whether a given DM model is already excluded.
Dark Matter Parameters
Ο‰Cen Halo Profile & J-Factor
J-Factor (log₁₀)
β€”
GeV² cm⁻⁡ sr
Brown et al. 2019 reference
18.3 β€” 19.1
NFW, ψ = 0.5°, depending on tidal history
Fermi-LAT dSph median
18.8
Classical dwarf spheroidals (ψ = 0.5°)
Reticulum II (best dSph)
19.6
Highest J-factor confirmed dSph target
Predicted Flux Ξ¦_Ξ³
β€”
ph cm⁻² s⁻¹ (E > E_th)
vs Fermi-LAT Limit
β€”
Upper limit ratio Ξ¦/Ξ¦_lim
vs CTA Projected
β€”
Ξ¦ / CTA sensitivity
Detection Status
β€”
Flux vs DM Particle Mass (current βŸ¨Οƒv⟩ & profile)
Observatory Limits & Sensitivities at Current Parameters
Instrument Energy Range Exposure βŸ¨Οƒv⟩ Limit / Sensitivity Status

The differential gamma-ray flux from DM self-annihilation is Ξ¦_Ξ³ = (βŸ¨Οƒv⟩ / 8Ο€ m_χ²) Γ— dN/dE Γ— J(ψ), where J(ψ) = ∫∫ ρ²(r) dl dΞ© is the astrophysical J-factor β€” the line-of-sight integral of the DM density squared over the integration solid angle ψ.

The J-factor is the dominant source of astrophysical uncertainty. For Ο‰Cen, Brown et al. (2019, ApJ 877:L43) estimate log₁₀(J) β‰ˆ 18.3–19.1 (GeVΒ² cm⁻⁡ sr) at 0.5Β° integration angle, depending on assumptions about how much of the original dwarf galaxy's DM halo survived tidal stripping. An NFW (Navarro-Frenk-White) profile with a central cusp gives the highest J-factor; a Burkert core profile gives ~10Γ— lower; tidal stripping models reduce it further.

The canonical thermal relic cross-section βŸ¨Οƒv⟩ β‰ˆ 3Γ—10⁻²⁢ cmΒ³/s is the value that naturally produces the observed DM abundance via freeze-out. Many theories predict this value. Fermi-LAT has excluded this cross-section for DM particles lighter than ~100 GeV in bΜ„b for several dSphs; Ο‰Cen constraints are comparable.

The bbΜ„ channel is the default for WIMP annihilation, producing a broad gamma-ray spectrum peaked at ~m_Ο‡/20. W⁺W⁻ gives a slightly harder spectrum; ttΜ„ is kinematically available only above m_Ο‡ > m_top β‰ˆ 173 GeV. The Ξ³Ξ³ (line signal) channel is suppressed at tree-level but gives a striking mono-energetic line at E = m_Ο‡ β€” a definitive WIMP signature if detected.

Flux is integrated above E_threshold = m_Ο‡/20 for continuum channels, or at E = m_Ο‡ for the line. Fermi-LAT limits apply in the 0.1–300 GeV range; CTA will extend to multi-TeV energies with ~10Γ— better sensitivity at 1 TeV.

This tool is a simplified model for exploration. Detailed spectral analysis requires full likelihood methods, energy-dependent effective areas, and exposure maps. See Fermi-LAT Collaboration (2022) for Ο‰Cen-specific limits.

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